The relationship between sleep and general anesthesia is of great clinical relevance given the high prevalence of patients with sleep disorders or insufficient sleep undergoing major surgery. To date, there is an incomplete understanding of how mechanisms that regulate anesthetic state transitions and sleep homeostasis interact. The preoptic region is a critical node for sleep regulation. The median preoptic nucleus (MnPO) regulates both state transitions and sleep homeostasis, making it a key, yet virtually unexplored, substrate for sleep- anesthesia interactions. Preliminary data obtained for this application suggest that distinct neuronal subpopulations within MnPO control the transition to and from general anesthesia as well as sleep-wake oscillations. Our long-term goal is to understand the neurobiological and clinical relationship between sleep and general anesthesia. The goal of the proposed studies is to examine the role of GABAergic and glutamatergic neurons in the MnPO and ventrolateral preoptic nucleus (VLPO) in sleep homeostasis and general anesthesia. The proposed studies will use Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to test the hypothesis that the MnPO is a primary site for arousal state control, and that GABAergic and glutamatergic neurons in the MnPO regulate different aspects of sleep-wake states and general anesthesia. Aim 1 will use DREADDs for selective activation of GABAergic and glutamatergic neurons in the MnPO and VLPO to probe a causal relationship in controlling anesthetic induction, emergence, and post- anesthesia sleep-wake behaviors. In a second set of experiments we will test whether DREADD manipulations of MnPO and VLPO differentially alter corticocortical functional connectivity during wakefulness and general anesthesia. Aim 2 will assess the role of GABAergic and glutamatergic neurons in the MnPO and VLPO in sleep-wake regulation. Analysis of c-Fos immunoreactivity will reveal putative downstream targets of MnPO and VLPO neurons in sleep/wake-related areas. Additional experiments will determine whether activation of GABAergic neurons in the MnPO during general anesthesia can accelerate the anesthetic- induced recovery of sleep debt accrued during previous sleep deprivation. The proposed experiments will significantly advance our understanding of the mechanisms that regulate sleep-anesthesia interactions. These data will also provide a novel paradigm of how a single brain region (in this case, the MnPO) can control anesthetic induction and emergence through GABAergic and glutamatergic mechanisms, respectively.